Direct Air Contact Liquid Cooling System Heat Exchanger Assembly

ABSTRACT

A compact heat exchanger assembly for use in hybrid liquid-air cooling system adapted to provide a liquid cooling mechanism for components or adapter boards in a personal computer system. The heat exchanger assembly consists of a heat exchanger chamber, though which the thermal transfer liquid flows. An air pump injects air bubbles into the heat exchanger chamber through a porous material. The air bubbles rise up through the thermal transfer liquid and exit at the top of the heat exchanger chamber through a semi-permeable membrane which inhibits loss of the thermal transfer fluid. As the air bubbles pass through the thermal transfer liquid, heat is exchanged directly between the thermal transfer liquid and the contained air. The heat is then removed from the system as the heated air is expelled from the heat exchanger chamber. A valve assembly prevents the thermal transfer liquid from entering the air pump in the event air flow through the heat exchanger chamber is stopped.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to, and claims priority from, U.S.Provisional Patent Application Ser. No. 60/917,965 filed on May 15,2007, which is herein incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

The present invention is related generally to cooling systems associatedwith component circuit boards such as those installed in expansion slotsof personal computer systems, and specifically, to a hybridliquid-to-air cooling system adapted for use in cooling integratedcircuit components, such as graphics processing units, installed on acomponent circuit board.

Personal computer systems which are design for desktop or under-deskuse, and which are typically characterized by a main-board ormotherboard housed in a chassis or case, often provide one or moreexpansion slots into which auxiliary components may be installed. Theseauxiliary components may include network adapter circuit boards, modems,specialized adapters, and graphics display adapters. These auxiliarycomponents may receive power through the connection to the motherboard,or through additional connections directly to a system power supplycontained within the chassis or case. Additional components, such ashard drives, disk drives, media readers, etc. may further be containedwithin the chassis or case, and coupled to the system power supply andmotherboard as needed.

During operation, the motherboard and various auxiliary componentsconsume power and generate heat. To ensure proper functionality of thecomputer system, it is necessary to regulate the operating temperaturesinside the environment of the chassis or case. Individual integratedcircuits, especially memory modules and processors, may generatesignificant amounts of heat during operation, resulting in localized hotspots within the chassis environment. The term “processors”, as usedherein, and as understood by one of ordinary skill in the art, describesa wide range of components, which may include dedicated graphicsprocessing units, microprocessors, microcontrollers, digital signalprocessors, and general system processors such as those manufactured andsold by Intel and AMD. Failure to maintain adequate temperature controlthroughout the chassis environment, and at individual integratedcircuits, can significantly degrade the system performance and mayeventually lead to component failure.

Traditionally, one or more cooling fans are associated with the systempower supply, to circulate air throughout the chassis environment, andto exchange the high temperature internal air with cooler external air.However, as personal computer systems include increasing numbers ofindividual components and integrated circuits, and applications becomemore demanding on additional processing components such as graphicsdisplay adapters, a system power supply cooling fan may be inadequate tomaintain the necessary operating temperatures within the enclosedchassis environment.

Specialized liquid cooling systems are available for some components ina personal computer system. Specialized liquid cooling systems typicallyrequired a coolant circulation pathway through which a coolant orthermal transfer liquid, often driven by an impeller is circulated. Thecirculation pathway routes the thermal transfer liquid between a heatexchanger such as a radiator and a heat source, such as a CPU, GPU,microprocessor or transformer. Specialized liquid cooling systems arewell adapted for maintaining adequate operating temperatures forindividual components. However, these specialized liquid cooling systemsare not easily adapted for use with a wide variety of components oradapter boards in a personal computer system, and are often bulky andnoisy during operation.

Accordingly, it would be advantageous to provide a hybrid liquid-aircooling system which may be easily adapted to provide a compact andquiet liquid cooling mechanism for use with a wide range of componentsor adapter boards in a personal computer system, and which functionscooperatively with an air cooling system.

BRIEF SUMMARY OF THE INVENTION

Briefly stated, the present disclosure provides a compact heat exchangerassembly for use with hybrid liquid-air cooling system which isgenerally adapted to provide a liquid cooling mechanism for use with awide range of semiconductor components or adapter circuit boardsinstalled in a personal computer system, and which functionscooperatively with an air cooling system. The heat exchanger assemblyconsists of a heat exchanger chamber, though which the thermal transferliquid pass during circulation through the cooling system. As thethermal transfer liquid passes through the heat exchanger, an air pumpinjects air bubbles into the heat exchanger chamber through a porousmaterial. The air bubbles rise up through the thermal transfer liquidand exit at the top of the heat exchanger chamber through asemi-permeable membrane which inhibits loss of the thermal transferfluid. As the air bubbles pass through the thermal transfer liquid, heatis exchanged directly between the thermal transfer liquid and thecontained air. The heat is then removed from the system as the heatedair is expelled from the heat exchanger chamber. A valve assemblyprevents the thermal transfer liquid from entering the air pump in theevent air flow through the heat exchanger chamber is stopped.

The present disclosure further provides a method for removing heat froma thermal transfer liquid circulating within a liquid cooling systemadapted for use with a wide range of semiconductor components or adaptercircuit boards installed in a personal computer system. Heated thermaltransfer liquid is circulated into a heat exchanger assembly, includinga heat exchanger chamber. Lower temperature air is injected into theheat exchanger chamber through a porous material by a pump. Risingthrough the heated thermal transfer liquid within the heat exchangerchamber, the air bubbles absorb thermal energy from the thermal transferliquid. Heated air is released from the heat exchanger chamber via asemi-permeable membrane at the top of the heat exchanger chamber anddischarged into the external environment, removing thermal energy fromthe system. The cycle is repeated as the thermal transfer liquid iscirculated between one or more heat sources and the heat exchangerchamber.

The foregoing features, and advantages set forth in the presentdisclosure as well as presently preferred embodiments will become moreapparent from the reading of the following description in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the accompanying drawings which form part of the specification:

FIG. 1 is a fluid circuit diagram of the liquid cooling system heatexchanger assembly of the present disclosure; and

FIG. 2 is a fluid circuit diagram of an alternate embodiment heatexchanger of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughoutthe several figures of the drawings. It is to be understood that thedrawings are for illustrating the concepts set forth in the presentdisclosure and are not to scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description illustrates the invention by way ofexample and not by way of limitation. The description enables oneskilled in the art to make and use the present disclosure, and describesseveral embodiments, adaptations, variations, alternatives, and uses ofthe present disclosure, including what is presently believed to be thebest mode of carrying out the present disclosure.

Turning to FIG. 1, a liquid cooling system heat exchanger assembly 100of the present disclosure, for use with electronic components such asthose found in a personal computer consists generally of one or morecold plates 102 disposed in contact with heat sources 104, and anassociated circulating liquid coolant flow pathway 106 within whichflows a thermal transfer fluid 107. The liquid coolant flow pathway 106includes a liquid pump 108 and/or fluid reservoir, and is operativelycoupled to deliver a flow of heated thermal transfer fluid 107 to adirect air contact heat exchanger 110 for extracting absorbed heat fromthe thermal transfer fluid 107. Generally, the liquid coolant flowpathway 106 consists of one or more tubes or pipes, which contain thecirculating thermal transfer fluid 107, and which are configured toprovide a circulating flow pathway between each cold plate 102 and theheat exchanger 110.

During operation, the thermal transfer fluid 107 circulates through thecoolant flow pathways 106, drawing heat away from the heat sources 104through the associated cold plates 102, and dissipating the heatdirectly to air bubbles formed within the heat exchanger 110 fordischarge out of the system as the thermal transfer fluid 107 flowsthrough the direct air contact heat exchanger 110.

In an embodiment of the present invention, the direct air contact heatexchanger 110 is configured to facilitate a direct exchange of heatbetween the thermal transfer fluid 107 and lower temperature ambientair. The heat exchanger 110 consists of a vessel 200 defining a heatexchanger chamber 202, having at least one fluid flow inlet 204 and atleast one fluid flow outlet 206. Thermal transfer fluid 107 circulatingin the cooling system 106 is routed into the fluid flow inlet 204, andexits the heat exchanger chamber 202 through the fluid flow outlet 206.At the base 210 of heat exchanger chamber 202, an air insertion assembly212 consists of a porous material 214 which permits forced entry ofbubbles 216 of the ambient air. The ambient air is forced through theporous material 214 from an external air intake 218 by means of an airpump 220. A suitable backflow diverter or directional valve 222 preventsany thermal transfer fluid 107 which may pass through the porousmaterial 214, from flowing back into the air pump 220 and draining fromthe system via the air intake 218.

While the present disclosure illustrates and describes the heatexchanger chamber 202 as having a base and a top, defined with respectto the direction of gravity, those of ordinary skill in the art willrecognize that a variety of different configurations for the heatexchanger chamber 202 may be utilized which do not require the chamber202 to be oriented with respect to gravity for proper operation, butwhich still enable the introduction and removal of ambient air bubbles216 to a circulating flow of thermal transfer liquid 107.

As the ambient air bubbles 216 move through the thermal transfer fluid107 in the heat exchanger chamber 202, the boundary surfaces between thethermal transfer fluid 107 and the ambient air bubbles 216 provides alarge contact region and an optimal low thermal resistance contactbetween the fluid and the air, allowing thermal energy (heat) totransfer rapidly between the thermal transfer fluid 107 and the bubbles216 of ambient air. As the air bubbles 216 exit the heat exchangerchamber 202, the released air removes the thermal energy (heat) from thecooling system.

As the air bubbles 216 rise through the thermal transfer fluid 107 inthe heat exchanger chamber 202, they additionally absorb significantquantities of moisture from the thermal transfer fluid 107, oftenreaching near 100% humidity. In one embodiment, at the top of the heatexchanger chamber 202, a semi-permeable membrane 224 permits the bubbles216 of air to exit the heat exchanger chamber 202 through an exhaustport or air outlet 226, while simultaneously preventing the absorbedthermal transfer fluid 107 from exiting out the exhaust port or airoutlet 226.

In an alternate embodiment, shown in FIG. 2, the thermal transfer fluiddoes not completely fill the heat exchanger chamber 202, and the airbubbles 216 rising through the thermal transfer fluid 107 are containedat the top of the heat exchanger chamber 202, where a plurality ofcondensation fins 300 extend vertically downward from a top surface 302of the heat exchanger chamber 202. Moisture 304 from the thermaltransfer fluid 107 trapped in the rising bubbles 216 of air condensesonto the surfaces of the condensation fins 300, and drips back into thevolume of thermal transfer fluid 107 within the heat exchanger chamber202. The heated and dried air accumulated adjacent the top surface 302of the heat exchanger chamber 202 then circulates out of the systemthrough the air outlet 226.

Those of ordinary skill in the art will recognize that the specificshape and arrangement of the heat exchanger 202, inlets 204, outlets206, exhaust ports 226, and ambient air entry ports 218 may be adaptedto accommodate the particular application for which the cooling systemis configured. For example, the heat exchanger chamber may becylindrical in shape, axially aligned with the direction of gravity. Thefluid flow inlet near may be positioned adjacent the base of the heatexchanger chamber, and the fluid flow outlet near the top, resulting inan upward flow of thermal transfer fluid through the heat exchangerchamber. The ambient air entry port may be centrally disposed in thebase, and the top end of the cylindrical chamber may define the exhaustport, such that bubbles of ambient air injected into the heat exchangerchamber at the base travel upward through the flow of thermal transferfluid, and exit at the top through the exhaust port.

As various changes could be made in the above constructions withoutdeparting from the scope of the disclosure, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

1. A liquid cooling system adapted to provide a direct air contactliquid cooling mechanism, comprising: a pathway for circulating a flowof thermal transfer fluid between at least one heat source and a heatexchanger; and wherein said heat exchanger is configured to facilitate adirect transfer of heat from the thermal transfer fluid to air bubblespassing through the heat exchanger.
 2. The liquid cooling system ofclaim 1 wherein said heat exchanger includes a heat exchanger chamberhaving at least one inlet for receiving a flow of thermal transferfluid, at least one outlet for discharging a flow of thermal transferfluid, an air insertion assembly for receiving a supply of ambient air;and at least one air exhaust port for evacuating heated air which haspassed through said flow of thermal transfer fluid within said heatexchanger chamber and absorbed thermal energy there from.
 3. The liquidcooling system of claim 2 wherein said air insertion assembly includes aporous material disposed between a source of ambient air and said heatexchanger chamber, said porous material generally permitting passage ofsaid ambient air and generally preventing passage of said thermaltransfer fluid; and an air pump configured to direct a flow of ambientair through said porous material into said heat exchanger chamber. 4.The liquid cooling system of claim 3 wherein said air insertion assemblyfurther includes a back flow valve configured to prevent a flow ofthermal transfer fluid from exiting said heat exchanger chamber throughsaid air pump.
 5. The liquid cooling system of claim 2 wherein said atleast one exhaust port is separated from said heat exchanger chamber bya semi-permeable membrane, said semi-permeable membrane configured topass a flow of air and to exclude a flow of thermal transfer fluid. 6.The liquid cooling system of claim 2 wherein said heat exchanger chamberincludes a plurality of moisture condensation fins extending from atleast an upper inner surface of said heat exchanger chamber into apocket of contained air disposed between said upper inner surface ofsaid heat exchanger chamber and a volume of thermal transfer fluidcontained within said heat exchanger chamber, said moisture condensationfins configured to facilitate the condensation of moisture from saidentrapped air.
 7. The liquid cooling system of claim 1 wherein saidpathway for circulating a flow of thermal transfer fluid and said heatexchanger are adapted for use in a personal computer system.
 8. Theliquid cooling system of claim 1 wherein said pathway for circulating aflow of thermal transfer fluid is a closed loop pathway, and includes atleast one means for imparting a flow to said thermal transfer fluidwithin said pathway.
 9. A method for extracting heat from a thermaltransfer fluid circulating within a liquid cooling system, comprising:circulating a flow of said thermal transfer fluid through a heatexchanger chamber, said circulating flow including the introduction ofheated thermal transfer fluid to said heat exchanger chamber and thedischarge of cooled thermal transfer fluid from said heat exchangerchamber; injecting bubbles of ambient air into said heat exchangerchamber, said bubbles of ambient air passing through said circulatingflow of thermal transfer fluid contained within said heat exchangerchamber and extracting heat from said introduced heated thermal transferfluid at the direct fluid-air interface of each bubble to cool saidthermal transfer fluid; extracting heated ambient air from said heatexchanger chamber for discharge to an external environment.
 10. Themethod of claim 9 wherein said heated ambient air is extracted from saidheat exchanger chamber through a semi-permeable membrane, saidsemi-permeable membrane configured to pass a flow of heated air, but toexclude a flow of thermal transfer fluid.
 11. The method of claim 9further including the step of reducing the moisture content of said flowof heated air prior to extracting said heated ambient air from said heatexchanger chamber.
 12. The method of claim 11 further include the stepof condensing moisture from said flow of heated air; and returning saidcondensed moisture to said circulating flow of thermal transfer fluid.13. A method for thermal regulation of an electronic component radiatingthermal energy, including: providing a flow of thermal transfer fluid inthermal contact with said electronic component, whereby thermal energyradiated from said electronic component is transferred to said flow ofthermal transfer fluid; delivering said flow of thermal transfer fluidcarrying said transferred thermal energy to a direct air-fluid heatexchanger assembly having a heat exchanger chamber; injecting bubbles ofair into said flow of thermal transfer fluid within said heat exchangerchamber, said bubbles of ambient air passing through said flow ofthermal transfer fluid and extracting thermal energy from said thermaltransfer fluid across a direct fluid-air interface at each bubble tocool said flow of thermal transfer fluid; discharging said heatedbubbles of air from said heat exchanger chamber whereby said extractedthermal energy is removed from said flow of thermal transfer fluid. 14.The method of claim 13 further including the step of recirculating saidflow of thermal transfer fluid into thermal contact with said electroniccomponent after extraction of said thermal energy within said heatexchanger chamber.
 15. The method of claim 13 further including the stepof dehumidifying said heated bubbles of air prior to discharge from saidheat exchanger chamber, whereby absorbed moisture is returned to saidflow of thermal transfer fluid.